It is known that a minute deformed region of which a refractive index is different from that of the vicinity thereof is formed if short pulse laser is condensed inside a transparent medium such as quartz glass. A technique has been examined in which a plurality of such minute deformed regions are formed inside the medium in a three-dimensional manner and are used for recording information. PTLs 1 and 2 and NPLs 1 and 2 disclose a three-dimensional memory in which a recording mark with a refractive index different from that of peripheral glass is locally formed in glass or the like. A mechanism in which local deformation occurs due to short pulse laser is disclosed in, for example, NPL 3. NPL 3 discloses a technique in which a plurality of light spots are formed by using a femtosecond laser and a spatial phase modulator, and an optical waveguide is formed inside a transparent material such as quartz glass. The continuity of the waveguide is improved by changing the number of pattern elements of the light spots depending on a shape of the formed waveguide. In addition, NPL 4 discloses a technique in which simultaneous multi-bit recording in fused silica (quartz glass) is performed by using a femtosecond laser and a spatial phase modulator, and shows a result of quantitative evaluation using SNR.